Abstract

The interactions of N-piperidineethyl-functionalized indene compounds 1-R-S-C5H10NCH2CH2C 9H6 (R = H- (1), Me3Si- (2)) with lanthanide(III) amides [(Me3Si)2N]3Ln(μ-Cl) Li(THF)3 (Ln = Yb, Eu, Sm, Nd) were studied. The results indicated that the ligands and reductive potentials of Ln3+/Ln2+ have an influence on the reaction patterns and the coordination mode of the indenyl ligands with the central metals. Reactions of [(Me3Si) 2N]3Ln(μ-Cl)Li(THF)3 (Ln = Yb, Eu) with 2 equiv of corresponding indene compounds 1-R-3-C5H 10NCH2CH2C9H6 (R = H- (1), Me3Si- (2)) produced organolanthanide(II) complexes [η5:η1C5H10NCH 2C9H6]2LnII (Ln = Yb (3), Eu (5)) and novel organolanthanide(II) complexes with general formula [η4:η2:η1-(C5H 10NCH2CH2C9H5SiMe 3)Li(μ-Cl)]LnII(η5:η1- C5H10NCH2-CH2C9H 5SiMe3) (Ln = Yb (4), Eu (6)), and a new highly conjugated bis(N-piperidineethyl)-dibenzofulvalene, (C5H10NCH 2C9H5)2 (9), was unexpectedly isolated as a byproduct in the preparation of 6, indicating the ligands' effects on the coordination and reactivity patterns. Theoretical calculations on ytterbium(II) complexes having indenyl ligands indicated that the indenyl hapticity depends on the strain, steric, and electronic effects. Treatment of lanthanide(III) amides [(Me3Si)2N]3Ln(μ-Cl) Li(THF)3 (Ln = Sm, Nd) with 2 equiv of C5H 10NCH2CH2C9H7 (1) afforded indenyl lanthanide(III) complexes with general formula [η3-C5H10NCH2CH 2C9H6]2LnIII[η 3:η1-C5H10NCH2CH 2C9H6] (Ln = Sm (7), Nd (8)). The shortest distances involving the nonbridging atoms of the C5 portions of the indenyl groups indicated an allyl-like nature of the ligand-to-metal coordination. The interaction of [(Me3Si)2N] 3SmIII(μ-Cl)Li-(THF)3 with 2 equiv of 1-Me3Si-3-C5H10NCH2CH 2C9H6 (2) produced an unexpected bis(N-piperidineethyl)-dibenzofulvalene (C5H10NCH 2CH2C9H5)2 (9) and other unidentified solids, suggesting the ligands' influence on the reactivity patterns. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of compounds 4, 7, 8, and 9 were additionally determined by X-ray diffraction study. The catalytic activity of the organolanthanide complexes 3-8 on MMA polymerization was examined. It was found that the π-bonded tris(N-piperidineethylindenyl)lanthanide(III) complexes 7 and 8 exhibit unexpected good catalytic activity on MMA polymerization, and complex 7 also showed an unexpected high catalytic activity on ε-caprolactone polymerization. It was found that the catalytic activity of the complexes depended on the polymerization conditions. The solvents, temperatures, substituted groups, and lanthanide ionic radii effects on the catalytic activity of the complexes were examined. © 2007 American Chemical Society.